Update: Portland Commissioner Nick Fish, who oversees the Water Bureau, says dumping 38 million gallons of water is the "conservative but correct" decision. Read more.

Portland administrators will flush 38 million gallons of water from Mt. Tabor Reservoir 5 after a 19-year-old man urinated in the city’s drinking supply.

“Even though there is very minimal public health risk, the bottom line is that our commitment is to serve water that’s clean, cold and constant,” said Water Bureau administrator David Shaff. “That doesn’t include pee. Not from people, at least.”

The Portland Water Bureau has made public the video that prompted a security officer to call police Wednesday morning. Watch it here.

Around 1 a.m. Wednesday, the security officer who monitors video cameras at the reservoir complex spotted five people with skateboards “hanging out near the gatehouse,” Shaff said.

Three of the men headed toward Reservoir 5, the kidney-shaped landmark on the western flank of Mt. Tabor.

The camera caught one man as he stopped, leaned against the iron fence and, after a moment or two, hitched up his pants and pulled away from the bars, Shaff said.

“When you see the video, he’s leaning right up because he has to get his little wee wee right up to the iron bars. There’s really no doubt what he’s doing,” Shaff said.

“It’s stupid. You can see the sign that says: ‘This is your drinking water. Don’t spit, throw, toss anything in it.’ He’s four feet away from that sign. Unless he’s from North Dakota and just moved here, he’s got to know that’s our drinking water.”

The video also shows two men trying to climb the fence. One made it and may have stepped in the water -- “If so, he discovered that it’s really, uncomfortably cold,” Shaff said. Then the men spent some time taking cell phone pictures of themselves.

While the group was documenting its visit to the reservoir, a Water Bureau security officer and Portland Police officers headed in their direction. Police stopped a car on Southeast 69th Avenue near the east entrance to the park and cited three men on accusations of trespassing; one was also given a citation accusing him of public urination. Police have not released the names of those cited and have not decided whether to charge anyone with additional crimes.

The Water Bureau used to keep security guards on duty at the Mt. Tabor and Washington Park reservoirs around the clock. But those posts were cut several years ago in an attempt to limit rate increases.

Now the bureau has guards patrol all Water Bureau property, including the reservoirs, and officers who monitor reservoir security cameras from the city’s Emergency Operations Center in east Portland. Shaff said he does not believe having a security guard posted at Mt. Tabor would have sped the response Wednesday morning.

Water Bureau officials turned off the pipes that carry water to and from Reservoir 5 immediately. They expect test results on the water to come back Thursday, and to show no contamination or health risk.

Still, crews will flush the reservoir -- and give it a second spring cleaning on top of the one it received about a month ago -- over the next four to six days just to be safe and to reassure consumers.

Strange things end up in Portland’s water supply all the time, with minimal risk or impact to users. And this is not the first time human beings have attempted to interfere with the stuff that comes out of Stumptown taps: In 2008, a man and a woman caught skinny dipping in Mt. Tabor were sentenced to 16 hours of community service each.

Three years ago, the city flushed 8 million gallons of water after a 21-year-old Molalla man peed in Mt. Tabor Reservoir 1.

City officials estimated that flushing the water and cleaning up after that episode cost $35,000. Shaff said he wasn’t sure what this effort will cost. The current shutdown at Mt. Tabor won’t impact Portland water users, he said.

“Right now we’ve got 100-plus million gallons of day free flowing down the river because the Bull Run reservoirs are as full as they can be,” he said. “I’ve got tons of water available that doesn’t have human pee in it, so I’m going to replace this.”

The federal government has ordered Portland and other cities with open-air reservoirs to cover them. City leaders are waiting on results of a May ballot measure that could shift control of the Water Bureau from the City Council to a new independently elected board to decide how to proceed.